Code
B1275
LAND ROVER
B — Body
Potentiometer of the ventilation servo motor - short circuit to ground
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UK: 5
EN: 12
RU: 8
AI status
Completed
Completed
100%
Causes
- Damaged or chafed wiring harness shorting the potentiometer signal to ground
- Corroded, bent or pushed-back connector pins causing a ground short
- Failed ventilation servo motor / integrated potentiometer (internal short)
- Water ingress or contamination in actuator or connector
- Poor ground or body damage causing unintended continuity to chassis
- Faulty HVAC control module (rare)
Symptoms
- HVAC vent door(s) stuck, not moving or in wrong position
- HVAC mode/airflow selector not following commands
- DTC B1275 (potentiometer short to ground) stored in climate control module
- Inaccurate actuator position reading on a scan tool (signal near 0 V)
- Intermittent operation or loss of control after moisture exposure
What to check
- Read DTC(s) with a diagnostic scanner and note freeze-frame/live data for the HVAC actuator position PID
- Attempt to command the vent/door from the scanner and watch the potentiometer/position feedback value
- Visually inspect actuator, connector and wiring for damage, corrosion, water ingress and pin push-out
- Back-probe the actuator connector with ignition on and measure reference and signal voltages
- With harness disconnected, check continuity between the potentiometer signal pin and chassis ground (should be open)
- Wiggle the harness and connectors while observing live data to check for intermittent shorts
Signal parameters
- Reference (supply) voltage: typically ~5.0 V (present at actuator reference pin with ignition/ACU powered)
- Potentiometer signal voltage: variable ~0.5–5.0 V depending on door position; a short to ground will show ≈0 V
- Potentiometer resistance: typically in the low kilo-ohm range (manufacturer-specific) between end terminals; signal pin will vary between ends
Diagnostic algorithm
- Connect a scan tool, record DTC B1275 and HVAC actuator live data; attempt to command actuator and observe signal value.
- Perform visual inspection of actuator, wiring and connector for damage, corrosion, water ingress and pin damage at the dash/bulkhead.
- With ignition ON, back-probe the connector: verify reference (≈5 V) and measure the potentiometer signal voltage while commanding the actuator. If signal is ≈0 V constantly, suspect short to ground.
- Turn ignition OFF and disconnect actuator connector. Using a multimeter in continuity mode, check between signal pin and chassis ground. Continuity (near 0 Ω) indicates a short to ground in harness or actuator.
- If there is no continuity with the connector disconnected, perform harness isolation: inspect wiring runs, remove trim as needed and test continuity from the signal pin at the actuator connector back to the control module and for unintended grounds (shorts) to chassis.
- If wiring checks good, reconnect actuator and swap with a known-good actuator (if available) or install a replacement actuator to confirm fault follows the part.
- After repair, clear DTCs, re-test actuator operation and verify no return of the fault.
- If wiring and actuator are good but fault persists, inspect/replace HVAC control module or its connector as a last step (rare).
Likely causes
- Wiring harness damage at actuator or through bulkhead
- Failed/internally shorted HVAC servo motor potentiometer
- Corroded or contaminated connector at the actuator
Fault status
Status
Stored: Potentiometer/position sensor circuit for ventilation servo motor detected short to ground (signal ~0 V).
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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